Method for determining a writing power of a compact disc drive

ABSTRACT

A method for determining an optimum writing power of a compact disc drive includes representing the relationship between a target read-back signal parameter and writing power as a polynomial function, which is stored in a database. The optimum writing power is obtained after at least one iteration of a writing test procedure. The test procedure includes utilizing a constant writing power.

BACKGROUND OF INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a writing power control methodof a compact disc drive, and more specifically, the present inventiondiscloses a writing power control method capable of determining anoptimum writing power of a compact disc drive.

[0003] 2. Description of the Prior Art

[0004] In general, document management and storage is an importantconcern of companies and individuals. In the past, most documents wereprinted or written on paper but when the quantity of these documents islarge, the volume and weight of them becomes a problem. In parallel withthe development of computer technology, digitalized data is widely usedand stored by use of computer storage media. A wide variety of storagedevices is available for allowing users to store digital dataconveniently. A compact disc drive, which uses small, inexpensive andhigh capacity compact discs as storage media, is a popular and effectivestorage device.

[0005] Generally, before writing data onto a compact disc, the compactdisk drive must perform an optimum power control (OPC) to determine anappropriate writing power of the compact disc. As to a preferred methodof performing the OPC, details can be found in the Orange Book and aresummarized as follows.

[0006] Please refer to FIG. 1. FIG. 1 is a diagram of a compact disc 10when a compact disc drive performs the OPC on the compact disc 10according to the prior art. When the compact disc drive performs theOPC, a pick-up head 11 of the compact disc drive first retrieves anindicative optimum writing power P from a lead-in area 12 on the compactdisc 10. The indicative optimum writing power P is an appropriatewriting power of the compact disc 10 that a compact disc manufacturersuggests. Then, the pick-up head 11 uses fifteen writing powers, whichcomprises seven writing powers, P1 to P7, less than the indicativeoptimum writing power P, the indicative optimum writing power P itself,and seven writing powers, P8 to P14, greater than the indicative optimumwriting power P, to perform a writing procedure in fifteen successiveblocks 18 of the test area 16 of the compact disc 10.

[0007] After performing the writing procedure, the pick-up head 11 willretrieve a result written to the blocks 18 as a read-back signal. Theread-back signal is an AC coupled HF signal. The Orange Book has defineda symmetrical parameter β determined from the read-back signal. When thesymmetrical parameter β of the read-back signal corresponds to apredetermined requirement, the corresponding writing power can serve asthe actual optimum writing power of the compact disc 10. Afterretrieving the test results of the fifteen writing powers, the pick-uphead 11 obtains the symmetrical parameter β values (β values) of thefifteen read-back signals corresponding to the fifteen writing powers.Then, the compact disc drive compares the β values of the fifteenread-back signals with a target P value stored in the lead-in area 12 ofthe compact disc 10. If the smallest difference between thecorresponding P value of one of the fifteen writing powers and thetarget P value is less than a predetermined value, the writing powercorresponding to the above P value is the optimum writing power. If thedifferences between the corresponding P values of the fifteen writingpowers and the target P value are all greater than a predeterminedvalue, the fifteen writing powers are all unsuitable to function asactual writing powers Consequently, additional groups of fifteen writingpowers need to be selected to perform the optimum writing power controluntil an optimum writing power is obtained.

[0008] The aforementioned writing power control has two mainshortcomings. First, the method uses a trial and error approach withoutthe benefits of recursion. If the initial fifteen writing powersselected are inadequate, additional time must be spent in successivetrials. Second, the aforementioned writing power control utilizesdifferent writing powers during a short time interval. It is easy forthe pick-up head 11 to accidentally move to the next block to produce anincorrect etching depth during the writing test because of the unstablewriting power. As a result, erroneous P values may be obtained, whichfurther influences the accuracy of the determined optimum writing power,and ultimately writing quality.

SUMMARY OF INVENTION

[0009] It is therefore a primary objective of the claimed invention toprovide a writing power control method utilizing a polynomial functioncapable of determining an optimum writing power of a compact disc driveso as to solve the above-mentioned problems.

[0010] The claimed invention, briefly summarized, discloses a method fordetermining an optimum writing power of a compact disc drive. The methodincludes constructing a polynomial function which represents arelationship between a writing power and a target read-back signalparameter and retrieving a target read-back signal parameter from acompact disc and determining a corresponding first writing poweraccording to the polynomial function. Followed by, performing a writingtest procedure using the first writing power to determine a realread-back signal parameter and comparing the real read-back signalparameter with the target read-back signal parameter.

[0011] Subsequently, if a difference between the real read-back signalparameter and the target read-back signal is less than a predeterminedvalue, then writing data in the compact disc using the first writingpower. The method also includes, shifting the polynomial functionaccording to the real read-back signal parameter, and determining asecond writing power according to the shifted polynomial function andthe target read-back signal parameter. Additionally, performing awriting test procedure repeatedly, until the difference between the realand target read-back signal parameters is less than a predeterminedvalue.

[0012] It is an advantage of the claimed invention that the claimedoptimum writing power control method constructs a database of thewriting power and the read-back signal parameter in advance, andretrieves corresponding data of a polynomial function before writingdata onto a compact disc. Thus, a compact disc drive can quickly obtainthe optimum writing power through the target read-back parameter valuerecorded in the lead-in area of the compact disc.

[0013] These and other objectives of the claimed invention will no doubtbecome obvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0014]FIG. 1 is a diagram of a compact disc when a compact disc driveperforms an optimum power control to the compact disc according to theprior art.

[0015]FIG. 2 is a diagram of a common recordable compact disc (CD-R) orrewritable compact disc (CD-RW).

[0016]FIG. 3 is a graph of a polynomial function used for determining anoptimum writing power according to the present invention.

[0017]FIG. 4 is a diagram of a compact disc when a compact disc driveperforms a writing test procedure according to the present invention.

[0018]FIG. 5 is a modified graph of the polynomial function shown inFIG. 3.

[0019]FIG. 6 is a flowchart of a writing power control method accordingto the present invention.

DETAILED DESCRIPTION

[0020] Please refer to FIG. 2. FIG. 2 is a diagram of a commonrecordable compact disc (CD-R) or rewritable compact disc (CD-RW). Thecompact disc 20 is used to record data using a CD-R or CD-RW drive. Forthe purpose if this description a CD-R system will be used, employing βvalues for the read-back signal parameters, but this is not limiting anda CD-RW can also be used, employing γ values for the read-back signalparameters. The compact disc 20 comprises a power calibration area (PCA)22 for performing a writing test procedure, a lead-in area 24 whichrecords an indicative optimum writing power and a target read-backsignal parameter value (β value) of the compact disc 20, and a storagearea 26 for recording user data. The power calibration area 22 comprisesa count area 28 and a test area 30. The test area 30 comprises aplurality of blocks 32, and each block can be used for the writing testprocedure once. Furthermore, after the compact disc drive performs thewriting test procedure to fifteen blocks 32 of the test area 30, a countof the count area 28 is increased by one.

[0021] Please refer to FIG. 3. FIG. 3 is a graph of a polynomialfunction 40 a used in determining an optimum writing power according tothe present invention. The horizontal axis represents writing power, andthe vertical axis represents read-back signal parameter β. The presentinvention utilizes the polynomial function 40 a which represents arelationship between the writing power and the target read-back signalparameter β. A target β value is stored in the lead-in area 24 of thecompact disc 20.

[0022] The β value of the read-back signal (AC coupled HF) of thecompact disc drive must be within tolerance of the target β value forthe writing power to be acceptable. The present invention utilizes thepolynomial function 40 a to obtain an appropriate writing power Paaccording to the target β. As shown in FIG. 3, if the target β value isβ a, a writing power Pa is obtained according to the polynomial function40 a.

[0023] Please refer to FIG. 4. FIG. 4 is a diagram of the compact disc20 when the compact disc drive performs a writing test procedureaccording to the present invention. After obtaining the writing powerPa, the compact disc drive can utilize the writing power Pa to performthe writing test procedure in the test area 30 of the compact disc 20 soas to obtain a corresponding read-back signal parameter value β b. Inthe preferred embodiment of the present invention, a power calibrationprocedure utilizes a constant writing power to perform the writing testprocedure to fifteen successive blocks among the blocks 32, and todetermine the real read-back signal parameter according to an averageresult of the read-back signal parameters obtained from the plurality ofmiddle blocks of the fifteen blocks or according to a single result of aread-back single parameter obtained from the middle block of the fifteenblocks .

[0024] When the pick-up head 21 moves to the middle blocks of thefifteen blocks, the outputted writing power Pa has become stable, andthe blocks 32 can thus receive the proper etching depth of the writingpower Pa. Accordingly, a reliable read-back signal parameter value β bis obtained.

[0025] Please refer to FIG. 3 again. After obtaining β b according tomethods of the present invention, the next step is to compare theread-back signal parameter value β b with the target read-back signalparameter value β a to determine if the writing power is acceptable. Ifa difference between the read-back signal parameter value β b and thetarget read-back signal parameter value β a is less than an allowableerror A that is, the read-back signal parameter value β b is locatedbetween β a+Δ and β a-as shown in FIG. 3, then the writing power Pa issuitable as the optimum writing power. However, if the differencebetween the read-back signal parameter value β b and the targetread-back signal parameter value β a is greater than the allowable errorΔ, the writing power Pa is unacceptable and requires adjustment. Thisadjustment is accomplished by modifying the polynomial function 40 a.

[0026] Please refer to FIG. 5. FIG. 5 is a modified graph of thepolynomial function 40 a shown in FIG. 3. As shown in FIG. 5, when theread-back signal parameter value β b is located outside of the allowableerror range β a+Δ˜β a−Δ, the polynomial function 40 a is shiftedvertically, in this case downward, by an amount equal to the differencebetween the read-back signal parameter value β b and the targetread-back signal parameter value β a. A new polynomial function 40 b isthus obtained. A new writing power Pb can now be obtained according tothe original target read-back signal parameter value β a and the shiftedpolynomial function 40 b. The writing power Pb is used to perform thewriting test procedure as shown in FIG. 4 to obtain a correspondingread-back signal parameter value β c. If the difference between theread-back signal parameter value β c and the target read-back signalparameter value β a is less than the allowable error Δ as shown in FIG.5, the writing power Pb is the desired optimum writing power. However,if the difference between the read-back signal parameter value β c andthe target read-back signal parameter value β a is greater than theallowable error Δ, the aforementioned procedure of shifting thepolynomial function and retesting the writing power is repeated untilthe difference between the read-back signal parameter and the targetread-back signal parameter value β a is less than the allowable error Δ.

[0027] It needs be specified that the polynomial function 40 a is storedin a database in advance, and the database comprises a plurality ofpolynomial functions. A given polynomial function is based on thematerial and rotational speed of the compact disc. In general, thepolynomial functions required for compact discs produced by differentmanufacturers are likely to be different, as well as compact discsproduced by the same manufacturer under different rotational speeds.Each polynomial function is generated utilizing experimental data and apolynomial curve fitting method. Accordingly, the database of polynomialfunctions is constructed using this empirical data. The database can bestored in a computer system or the compact disc drive itself forretrieval of the related polynomial function when recording data to acompact disc.

[0028] Please refer to FIG. 6. FIG. 6 is a flowchart of the writingpower control method according to the present invention, and can besummarized as follows.

[0029] Step 100:Construct the appropriate polynomial function from thedatabase;

[0030] Step 102:

[0031] Retrieve the target read-back signal parameter value of thecompact disc 20 from the lead-in area 24;

[0032] Step 104:

[0033] Determine a writing power corresponding to the target read-backsignal parameter value according to the polynomial function;

[0034] Step 106:

[0035] Perform a writing test procedure on the compact disc using thewriting power to determine a real read-back signal parameter valueaccording to an average result of the read-back signal parametersobtained from the plurality of middle blocks of the successive blocks 32or according to a single result of the read-back signal parameterobtained from the middle block of the successive blocks 32;

[0036] Step 108:

[0037] Is the difference between the real read-back signal parameter andthe target readback signal parameter less than a predetermined value? Ifyes, perform step 114. If no, perform step 110;

[0038] Step 110:

[0039] Shift the polynomial function according to the difference betweenthe real readback signal parameter and the target read-back signalparameter;

[0040] Step 112:

[0041] Determine another writing power and perform step 106 according tothe shifted polynomial function and the target read-back signalparameter value;

[0042] Step 114:

[0043] The writing power is the desired optimum writing power.

[0044] The compact disc drive can thus obtain quickly and precisely theoptimum writing power.

[0045] In contrast to the prior art, the present writing power controlmethod constructs a database of writing powers and read-back signalparameters in advance, and retrieves a corresponding polynomial functionfrom this database before writing data onto a compact disc. Thepolynomial function is used in an iterative process to shorten the timerequired in determining the optimum writing power of the compact discdrive. Furthermore, the present optimum writing power control methoduses a constant writing power during the writing power test procedure.Maintaining a constant writing power during the course of the testprocedure improves the accuracy of the determined optimum writing powerand writing quality.

[0046] Those skilled in the art will readily observe that numerousmodifications and alterations of the device may be made while retainingthe teachings of the invention. Accordingly, the above disclosure shouldbe construed as limited only by the metes and bounds of the appendedclaims.

What is claimed is:
 1. A writing power control method of a compact discdrive for determining the writing power used for writing data onto acompact disc; the writing power control method comprising:(a)constructing a polynomial function which represents a relationshipbetween a writing power and a target read-back signal parameter;(b)retrieving the target read-back signal parameter from the compactdisc; (c)determining a first writing power corresponding to the targetread-back signal parameter according to the polynomial function;(d)performing a writing test procedure using the first writing power todetermine a real read-back signal parameter; (e)comparing the realread-back signal parameter with the target read-back signal parameter;and (f)if a difference between the real read-back signal parameter andthe target read-back signal parameter is less than a predeterminedvalue, writing data in the compact disc using the first writing power.2. The writing power control method of claim 1 wherein if the differencebetween the real read-back signal parameter and the target read-backsignal parameter is greater than the predetermined value, step(e)further comprises shifting the polynomial function according to the realread-back signal parameter, determining a second writing power accordingto both the shifted polynomial function and the target read-back signalparameter, and performing the writing test procedure again until thedifference between the real and target read-back signal parameters isless than the predetermined value.
 3. The writing power control methodof claim 1 wherein the compact disc comprises a power calibration area(PCA) for performing the writing test procedure to determine the writingpower.
 4. The writing power control method of claim 3 wherein the powercalibration area comprises a test area for performing the writing testprocedure and a count area for recording an execution number of thewriting test procedure, the test area comprises a plurality of blocks,each block is capable of performing the writing test procedure once, andthe writing test procedure comprises: selecting successive blocks fromthe test area; performing the writing test procedure on the successiveblocks using the first writing power; and determining the real read-backsignal parameter according to an average result of read-back signalparameters obtained from a plurality of middle blocks of the successiveblocks.
 5. The writing power control method of claim 3 wherein the powercalibration area comprises a test area for performing the writing testprocedure and a count area for recording an execution number of thewriting test procedure, the test area comprises a plurality of blocks,each block is capable of performing the writing test procedure once, andthe writing test procedure comprises: selecting successive blocks fromthe test area; performing the writing test procedure on the successiveblocks using the first writing power; and determining the real read-backsignal parameter according to a single result of a read-back signalparameter obtained from the middle block of the successive blocks. 6.The writing power control method of claim 1 wherein the compact discdrive is a CD-R drive, and the target read-back signal parameter is a Pvalue of a read-back signal according to a specification of the CD-Rdrive.
 7. The writing power control method of claim 1 wherein thecompact disc drive is a CD-RW drive, and the target read-back signalparameter is a y parameter of a read-back signal according to aspecification of the CD-RW drive.
 8. The writing power control method ofclaim 1 wherein the compact disc comprises a lead-in area, and thetarget read-back signal parameter is retrieved from data stored in thelead-in area.
 9. The writing power control method of claim 1 wherein thepolynomial function is constructed from a polynomial curve fittingmethod.
 10. A writing power control method of a compact disc drive fordetermining the writing power used for writing data onto a compact disc;the writing power control method comprising: (a)constructing apolynomial function which represents a relationship between a writingpower and a target read-back signal parameter; (b)retrieving the targetread-back signal parameter from the compact disc; (c)determining a firstwriting power corresponding to the target read-back signal parameteraccording to the polynomial function; (d)performing a writing testprocedure using the first writing power to determine a real read-backsignal parameter; (e)comparing the real read-back signal parameter withthe target read-back signal parameter; and (f)if a difference betweenthe real read-back signal parameter and the target read-back signalparameter is greater than the predetermined value, shifting thepolynomial function according to the real read-back signal parameter,determining a second writing power according to the shifted polynomialfunction and the target read-back signal parameter, and performing awriting test procedure again until the difference between the real andtarget read-back signal parameters is less than the predetermined valueto determine the writing power of the compact disc drive.
 11. Thewriting power control method of claim 10 wherein if the differencebetween the real read-back signal parameter and the target read-backsignal parameter is less than the predetermined value, step(e) furthercomprises writing data in the compact disc using the first writingpower.
 12. The writing power control method of claim 10 wherein thecompact disc comprises a power calibration area (PCA) for performing thewriting test procedure to determine the writing power.
 13. The writingpower control method of claim 12 wherein the power calibration areacomprises a test area for performing the writing test procedure and acount area for recording an execution number of the writing testprocedure, the test area comprises a plurality of blocks, each block iscapable of performing the writing test procedure once, and the writingtest procedure comprises: selecting successive blocks from the testarea; performing the writing test procedure on the successive blocksusing the first writing power; and determining the real read-back signalparameter according to an average result of read-back signal parametersobtained from a plurality of middle blocks of the successive blocks. 14.The writing power control method of claim 12 wherein the powercalibration area comprises a test area for performing the writing testprocedure and a count area for recording an execution number of thewriting test procedure, the test area comprises a plurality of blocks,each block is capable of performing the writing test procedure once, andthe writing test procedure comprises: selecting successive blocks fromthe test area; performing the writing test procedure on the successiveblocks using the first writing power; and determining the real read-backsignal parameter according to a single result of a read-back signalparameter obtained from the middle block of the successive blocks. 15.The writing power control method of claim 10 wherein the compact discdrive is a CD-R drive, and the target read-back signal parameter is a 0value of a read-back signal according to a specification of the CD-Rdrive.
 16. The writing power control method of claim 10 wherein thecompact disc drive is a CD-RW drive, and the target read-back signalparameter is a y value of a read-back signal according to aspecification of the CD-RW drive.
 17. The writing power control methodof claim 10 wherein the compact disc comprises a lead-in area, and thetarget read-back signal parameter is retrieved from data stored in thelead-in area.
 18. The writing power control method of claim 10 whereinthe polynomial function is constructed from a polynomial curve fittingmethod.